The purpose of this activity is to engage students in using mathematical strategies and knowledge of basic facts, to solve a problem in context.

The background knowledge and skills that should be established before and/or during this activity are outlined in the diagram below:

Click to show example questions for each heading

This activity may be carried out with step by step guidance, or by allowing the student to follow their own method of solution. The approach should be chosen in sympathy with students' skills and depth of understanding.

The average person in New Zealand travels by air for a total of 20 hours per year. This equates to 1000 kg of carbon added to the atmosphere by each person, each year.

A green initiative suggests that if everyone planted two trees a year, this will offset the carbon from air travel.

Assuming the average lifespan of a tree is 50 years, how much carbon does each tree offset, each year?

### The arithmetic approach (show more)

- The student is able to solve a context-based rates problem, using multiplicative strategies with guidance.

### The conceptual approach (show more)

- The student is able to solve a context-based rates problem, using multiplicative strategies.